The Riverton Post Office has four stations for service. Customers line up in single file for service on a FIFO basis. The mean arrival rate is 40 per hour, Poisson distributed, and the mean service time per server is 4 minutes, exponentially distributed. Compute the operating characteristics for this operation. Indicate whether the operation appears to be satisfactory in terms of the following:

(a) postal workers’ (servers’) idle time;

(b) customer waiting time and/or the number waiting for service; and

(c) the percentage of the time a customer can walk in and get served without waiting at all. LO.1